+
+/* Allow the caller to specify that two elements should be in the same
+ * equivalence class. If 'inverse' is TRUE, the elements are actually opposite
+ * to one another in some sense. This function will fail an assertion if the
+ * caller gives it self-contradictory data, ie if two elements are claimed to
+ * be both opposite and non-opposite. */
+void edsf_merge(int *dsf, int v1, int v2, int inverse);